Electrical protective device



Dec. 24, 1929. J. v. BREISKY 1,740,536

ELECTRICAL PROTECTIVE DEVICE Filed Feb. 1, 1924 wnusssss; mvaqnon Jbhn K Bre/s/ry" Patented Dec. 24, 1929 uNrr n STATES PATENT OFFICE JOHN V. BREISKY, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA ELECTRICAL PROTECTIVE nnvrcn Application filed February 1, 1924. Serial No. 690,015.

My invention relates to electrical protective devices and particularly to protective relays.

One object of my invention is to provide a relay that shall be particularly adapted for use in electrical systems that are protected in accordance with the phase-sequence currents.

Another object of my invention is to pro vide a relay that shall be substantially of constant impedance regardless of its current setting.

A further object of my invention is to pro vide a relay that shall be so adjustable that it shall present substantially the same 1111- pedance when traversed by energizing currents of differing magnitude.

My relay is particularly adapted for use in connection with impedance networks, such as are employed for distinguishing posltive, negative and zero phase-sequence currents. Such a network is shown and described in the application of C. LeG. Fortescue, and H. P. Sleeper, Serial No. 685,060, filed, January 8, 1924, and assigned to the Westinghouse Electric & Manufacturing Company. In such networks it is necessary that a relay shall have the same impedance as a given reactor or resistor in order that the proper angular distribution of the network currents may be had. In such networks, the relay constitutes one arm of an impedance bridge and, consequently, it its characteristics change, it would unbalance the bridge. It is customary to provide relays with current taps for various applications thereof. My relay has constant impedance with varlous current setting or tap adjustments and, consequently, is particularly adaptable tor such use.

In the accompanying drawings,

Figure 1 is a diagrammatic view of circuits and apparatus embodying my lnvention; and

Fig. 2 is a diagrammatic view of a modified form of circuits and apparatus embodying my invention. 4

In the several figures of the drawings, similar reference numerals indicate corresponding parts.

My invention comprises, in general, a relay 1 of the induction-motor type that is en ergized in accordance with the value of the current traversing a main circuit 2 for controlling an auxiliary circuit 3 that extends to any external apparatus such as the trip coil of a circuit interruptor (not shown).

The relay 1 comprises a core member 11 that has a plurality of pole pieces 12, 13 and 14. The pole pieces 12 and 13 are mounted the circuit 3 under predetermined operating conditions of the relay.

A coil 21 which surrounds the pole piece 14, constitutes the primary winding of the relay and is connected in the circuit 2. A second coil 22 surrounds the pole piece 14 and is connected in series with coils 23 and 24 that surround the pole pieces 12 and 13, respectively. Since the coil 22 is inductively related to the coil 21, the current traversing the same, and consequently that traversing the coils 23 and 24 will be out of phase with that traversing the coil 21. The magnetic fields incident to those out-of-phase currents co-operate with the disc 15 to cause it to turn under predetermined conditions. The corn struction'and operation of the induction relay is well known in the prior art and further details and description thereof is believed to be unnecessary; A variable resistor 25 is connected in series with the series connected coils 22, 23 and 24 to permit adjustment of the current setting of the relay.

Inthe operation of myrelay, the value 0 the current traversing the circuit 2 is controlled by any suitable means so that the re lay is operable over a predetermined range of current values. The current traversing the coil 21 acts as a primary winding for energizing the pole piece 14 and the core member 11. The coil 22 serves as a secondary winding adjacent to the coil 21 and is in ductively energized thereby, the current generated therein traversing the coils ..3 and 2 1 and, in turn, energizing the pole pieces 12 and 13, respectively. The value of the current traversing this circuit and consequently the torque on the armature member 15 may be varied by adjusting the variable resistor Since it is desired that the impedance of the relay 1 be maintained substantially constant for different tripping currents, the primary coil 21 must be left unchanged. The adjustment of the tripping current is accomplished by varying the adjustable resistor 25 in series with the coils 22, 23 and 24. If a greater tripping current is desired, the value of resistor 25 is increased. This decreases the current in the coils 23 and 24 and the resultant magnetic flux in the poles 12 and 13. Therefore, a greater current in the primary coil 21 is necessary to operate the relay. A change in the value of the resistance of the resistor 25 does not influence the impedance of the relay 1, because the voltage drop across the primary coil 21 is substantially unaffected by this change because of the relatively large air gaps in the magnetic circuit including the windings 21 and 22.

In the form of my relay shown in Fig. 2, a core member 31 of horseshoe-shape is employed that is energized by a primary coil that corresponds to the coil 21 in Fig. 1. The core member 31 terminates in pole pieces 33 and 3 1 for controlling the magnetic fields acting upon the disc 15. Shading coils 37 and 38 are mounted upon portions of the pole pieces 33 and 34:, respectively, and are con nected in series relation with a variable resistor 39. The secondary circuit defined by the coils 37 and 38 and the resistor 39 corresponds to the secondary circuit shown in Fig. 1 defined by the coils 22, 23 and 24 and the resistor 25. The operation of this form of my relay is identical with that shown in Fig. 1 except for the difference in shape of core members 11 and 31.

It will thus be seen that I have provided a relay that has substantially a constant impedance throughout its range of current adjustments and that, accordingly, is particularly adapted for use with impedance networks for electrical devices operating by phase-sequence currents. It is to be understood, however, that the use of my relay is not necessarily limited to that in connection with phase-sequence currents.

I do not Wish to be restricted to the specific circuit connections or arrangement of parts herein set forth, as various modifications thereof may be effected without departing from the spirit and scope of my invention. I desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

1. An induction relay comprising a disc armature, a core member having an air gap for the reception of said disc armature, eX- citing and adjusting windings on said core member, a variable resistance in series with said adjusting winding for varying the current therein to vary the value of current in the exciting winding required to actuate the armature, said air gap being of such magnitude that variations in the current in said adjusting winding effect substantially no change in the voltage across said exciting Winding.

2. The combination with a magnetic core member having a plurality of air gaps, a magnetizing coil therefor, and a rotatable member controlled thereby, of a second coil inductively related to the magnetizing coil, and a variable resistor in circuit with the second coil, said coils being adapted to cooperate with said core for establishing a rotating magnetic field cutting said rotatable member, said air gaps being of such length that the impedance of the ma netizing coil is sub stantially constant at all settings of said va riable resistor.

3. In a relay structure, a core member having opposed pole pieces separated by an air gap, a primary coil on one of said pole pieces for magnetizing-the core member, and adj ustable means for controlling the sensitivity of the relay comprising a secondary coil on another of said pole pieces and a variable resistor connected thereto, said coils being so arranged as to establish a travelling magnetic field, said air gap being of such length that variations of said resistor have substantially no effect on the impedance of said primary winding.

In testimony whereof, I have hereunto subscribed my name this 28th day of January, 1924.

JOHN V. BREISKY. 

